Radar systems are used to wirelessly detect the position of objects through the use of electromagnetic radiation. Frequency modulated continuous wave (FMCW) radar systems have become a common type of radar system. FMCW radars utilize a signal that continually changes frequency around a fixed reference frequency. Since the frequency of the signal continually changes with time, the frequency of a transmitted signal and a reflected signal will differ by a frequency that is proportional to the round trip time of the signal, giving a distance of a detected object.
FIG. 1A illustrates a block diagram of a typical FMCW radar system 100. FMCW radar system 100 comprises a transmission path and a reception path. A ramped signal generator 102 is configured to generate a ramped signal Sramp that is provided to a transmission chain 104 in the transmission path and a receive mixer 118 in the reception path. The transmission chain 104 generates a ramped RF signal that is transmitted as an electromagnetic wave 108 by a transmit antenna 106. Electromagnetic wave 108 reflects off of an object 110 as a reflected wave 112, which is returned to a reception antenna 114 that provides a reflected signal to a reception chain 116 that down-converts the reflected signal. The receive mixer 118 mixes the down-converted signal with the ramped signal Sramp to generate a signal having a frequency proportional to a position of the object 110, which is provided to a signal processing unit (SPU) 120.
FIG. 1B illustrates a timing diagram 122 showing operation of FMCW radar system 100. As shown in timing diagram 122, a transmitted signal 124 has a continually varying linear frequency ramp with a sawtooth waveform, while a reflected signal 126 has a continually varying linear frequency ramp with a sawtooth waveform that is offset in time from transmitted signal 124 by a round-trip time trt (corresponding to a frequency difference). The round-trip time trt is proportional to the object's distance from the FMCW radar system, so that SPU 120 can measure a distance based upon the time trt (e.g., dFMCW=(trt·c)/2).